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Article

Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility

1
Institute of Hygiene and Environmental Medicine, University Medicine, 17489 Greifswald, Germany
2
Biophysical Chemistry Department, Institute of Biochemistry, University of Greifswald, 17489 Greifswald, Germany
3
DOT GmbH Medical Implant Solutions, 18059 Rostock, Germany
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Current address: MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Rd, East Lansing, MI 48824, USA.
Academic Editor: Alina Vladescu
Coatings 2021, 11(9), 1118; https://doi.org/10.3390/coatings11091118
Received: 10 August 2021 / Revised: 7 September 2021 / Accepted: 10 September 2021 / Published: 15 September 2021
(This article belongs to the Special Issue Surface Modification of Medical Implants)
Unlike the native surface of the implant material (Ti6Al4V), oxidation with H2O2 leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with H2O2, strong differences in the PHMB adsorption capability between polished and corundum-blasted surfaces appear, indicating a roughness dependence. After NaOH treatment, no such effect was observed. The wetting properties of specimens treated with either H2O2 or NaOH prior to PHMB exposure clearly varied. To unravel the nature of this interaction, widespread in silico and in vitro experiments were performed. Methods: By X-ray photoelectron spectroscopy, scanning electron microscopy, water contact angle measurements and MD simulations, we characterized the interplay between the polycationic antimicrobial agent and the implant surface. A theoretical model for PHMB micelles is tested for its wetting properties and compared to carbon contaminated TiO2. In addition, quantitation of anionic functional group equivalents, the binding properties of PHMB with blocked amino end-group, and the ability to bind chlorhexidine digluconate (CHG) were investigated. Ultimately, the capability of osteoblasts to build calcium apatite, and the activity of alkaline phosphatase on PHMB coated specimens, were determined. Results: Simulated water contact angles on carbon contaminated TiO2 surfaces and PHMB micelle models reveal little influence of PHMB on the wetting properties and point out the major influence of remaining and recovering contamination from ambient air. Testing PHMB adsorption beyond the critical micelle concentration and subsequent staining reveals an island-like pattern with H2O2 as compared to an evenly modified surface with NaOH. Both CHG and PHMB, with blocked amino end groups, were adsorbed on the treated surfaces, thus negating the significant influence of PHMB’s terminal groups. The ability of osteoblasts to produce calcium apatite and alkaline phosphatase is not negatively impaired for PHMB mass coverages up to 8 μg/specimen. Conclusion: Differences in PHMB adsorption are triggered by the number of anionic groups and carbon contaminants, both of which depend on the specimen pre-treatment. With more PHMB covering, the implant surface is protected against the capture of new contamination from the ambient air, thus building a robust antimicrobial and biocompatible surface coating. View Full-Text
Keywords: Poly(hexamethylene)biguanide; PHMB; Molecular dynamics simulation; osseointegration; antimicrobial coating; wetting; Ti6Al4V; TiO2; Rose Bengal staining; water contact angle; carbon contamination; implant coating; micelle Poly(hexamethylene)biguanide; PHMB; Molecular dynamics simulation; osseointegration; antimicrobial coating; wetting; Ti6Al4V; TiO2; Rose Bengal staining; water contact angle; carbon contamination; implant coating; micelle
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MDPI and ACS Style

Zwicker, P.; Geist, N.; Göbler, E.; Kulke, M.; Schmidt, T.; Hornschuh, M.; Lembke, U.; Prinz, C.; Delcea, M.; Kramer, A.; Müller, G. Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility. Coatings 2021, 11, 1118. https://doi.org/10.3390/coatings11091118

AMA Style

Zwicker P, Geist N, Göbler E, Kulke M, Schmidt T, Hornschuh M, Lembke U, Prinz C, Delcea M, Kramer A, Müller G. Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility. Coatings. 2021; 11(9):1118. https://doi.org/10.3390/coatings11091118

Chicago/Turabian Style

Zwicker, Paula, Norman Geist, Elisabeth Göbler, Martin Kulke, Thomas Schmidt, Melanie Hornschuh, Ulrich Lembke, Cornelia Prinz, Mihaela Delcea, Axel Kramer, and Gerald Müller. 2021. "Improved Adsorption of the Antimicrobial Agent Poly (Hexamethylene) Biguanide on Ti-Al-V Alloys by NaOH Treatment and Impact of Mass Coverage and Contamination on Cytocompatibility" Coatings 11, no. 9: 1118. https://doi.org/10.3390/coatings11091118

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